DETERMINATION OF BITUMEN CONTENT BY CENTRIFUGE EXTRACTOR
1. Concept and Significance of “Determination of Bitumen Content”
The Centrifuge Extractor is used for the quantitative determination of bitumen in hot mixed paving mixtures and pavement samples, essentially as a field test to exercise quality control and ensure that the specified amount of bitumen has been used. The bitumen content is calculated by the difference in weight of the sample taken for the test.
2. Objectives
To determine the quantity of bitumen in hot-mix paving mixtures and pavement samples.
3. Apparatus
- Centrifuge extractor (revolving bowl inside a housing, cover plate with tightening nuts).
- Bowl housing with an outlet, mounted on an enclosed gear box.
- Splash lubricated gears and a system that is operated manually with a handle.
4. Procedure
- A sample of the asphalt mix was weighed.
- The sample was broken down into small pieces and heated.
- The sample was placed in a bowl, weighed, and a solvent was added.
- A beaker was placed under the outlet.
- The mixture was placed in the centrifuge and gradually rotated to increase the speed up to 3600 rpm. It was rotated until the solvent ceased to flow from the outlet.
- The centrifuge was stopped, solvent was added, and it was rotated again.
- The procedure was repeated until the extract was no longer cloudy.
- The content was dried and weighed.
5. Observation and Calculations
| Parameter | Weight (gm) |
|---|---|
| Before Test: Weight of sample (W1) | 43.5 gm |
| After Test: Weight of aggregate (WA) | 34.5 gm |
| After Test: Weight of extracted bitumen (WB) | 9.0 gm |
Calculation for Bitumen Content:
=
= 26.09%
6. Results
The bitumen content in the given sample was found to be 26.09%.
7. Conclusion and Discussion
Bitumen is used extensively in road construction as a binding material and water-proofing material. The amount of bitumen affects the strength and durability of pavement structures. The test effectively isolated the bitumen from the aggregate, allowing for an accurate quantitative determination of the binder content within the asphalt mix.